PGC-1α negatively regulates hepatic FGF21 expression by modulating the heme/Rev-Erbα axis

FGF21 is a hormone produced in liver and fat that dramatically improves peripheral insulin sensitivity and lipid metabolism. We show here that obese mice with genetically reduced levels of a key hepatic transcriptional coactivator, PGC-1 alpha, have improved whole-body insulin sensitivity with increased levels of hepatic and circulating FGF21. Gain-and loss-of-function studies in primary mouse hepatocytes show that hepatic FGF21 levels are regulated by the expression of PGC-1 alpha. Importantly, PGC-1 alpha-mediated reduction of FGF21 expression is dependent on Rev-Erb alpha and the expression of ALAS-1. ALAS-1 is a PGC-1 alpha target gene and the rate-limiting enzyme in the synthesis of heme, a ligand for Rev-Erb alpha. Modulation of intracellular heme levels mimics the effect of PGC-1 alpha on FGF21 expression, and inhibition of heme biosynthesis completely abrogates the down-regulation of FGF21 in response to PGC-1 alpha. Thus, PGC-1 alpha can impact hepatic and systemic metabolism by regulating the levels of a nuclear receptor ligand.